Targets utilized in a sputtering process have certain preferred characteristics. Among these are a high degree of uniformity insofar as the constituent materials of the target are concerned and a lack of significant voids in the target. A target not having these characteristics can easily result in non-uniformity of article coating, and uniformity is often an absolute requirement for certain articles and objects. This can result in very high waste costs.
Some sputtering applications call for the use of a target comprised of silicon and aluminum. Such a combination of elements has caused operational difficulties. Silicon-aluminum targets are typically formed by heating the silicon and aluminum to a high temperature and casting same in a mold.
Problems have been encountered in the process just described. First of all, it has been found that conventional casting techniques result in the formation of an unacceptable number of voids in the final casting. These voids are caused by gases formed during heating.
Furthermore, it has been found that the final casting often is not uniform throughout. That is, more specifically, it has been found that the aluminum component of the casting is not uniformly dispersed throughout the silicon component. The casting can include relatively large masses of aluminum embedded in an otherwise uniform mixture of silicon and aluminum. These masses and voids create, as mentioned above, significant problems when the cast product is utilized as a target when carrying out a sputtering process.